The present invention relates to a thrust reverser for a turbofan-type turbojet engine, more particularly such a thrust reverser having a deflector to control the direction and shape of the gases emanating from the thrust reverser.
Turbofan engines are well-known in the art and typically comprise a turbojet engine drivingly connected to a turbofan, usually mounted on the front of the turbojet engine. A turbofan housing, radially displaced from, but generally concentric with the turbofan engine housing, defines a cold flow air duct for air driven by the turbofan. In such turbofan engines having a relatively high bypass ratio, thrust reversers are typically provided on the turbofan housing so as to redirect the air passing through the cold flow air duct during landing of the aircraft in order to provide a reverse thrust.
Thrust reversers may assume many different configurations, but a typical thrust reverser is illustrated in FIG. 1. The thrust reverser comprises a stationary, upstream portion 1 which forms a part of the turbofan housing and defines an outer boundary of a cold flow air duct, a movable portion 2 which may redirect the air passing through the cold flow duct and a stationary, downstream collar 3 which also forms a portion of the turbofan housing. The stationary upstream portion 1 typically comprises an exterior panel 4 which defines a portion of the exterior surface of the turbofan housing, an internal panel 5 which, in conjunction with the housing for the turbojet engine (not shown) defines boundaries of the cold flow air duct and a frame 6 which interconnects panels 4 and 5. The frame 6 also provides support for the actuator 7a which controls the movement of the movable portion 2 which, in this instance, comprises one or more movable thrust reversing doors 7. The number of such doors may vary depending upon the application of the turbofan engine to a particular type aircraft and typically may comprise 2, 3 or 4 such doors. The doors may be located around the circumference of the turbofan housing and, when in their deployed or thrust reversing positions, redirect the air passing through the cold flow duct to provide a thrust reversing force. When in the closed, or forward thrust position, as illustrated in FIG. 1, the exterior panel 9 of the thrust reversing door 7 is flush with the outer surface of exterior panel 4 and the exterior surface of downstream collar 3 so as to provide a smooth aerodynamic surface for the air passing, over the exterior of the turbofan housing, illustrated by arrow 10.
FIG. 2 illustrates a pair of known thrust reversing doors 7 in their deployed is positions in which the forward, or upstream, edge is displaced radially outwardly from the generally annular turbofan housing. As is well-known in the art, rear, or downstream, portions of the thrust reverser doors 7 extend inwardly into the cold flow duct so as to redirect the air outwardly through the opening in the turbofan housing in a forward direction. Each thrust reverser door 7 is operatively associated with a hydraulic jack or actuator 7a, which typically comprises a cylinder having an extendable and retractable piston rod attached to the thrust reverser door 7.
The terms "upstream" and "downstream" are defined in relation to the direction of air or gas circulation in the forward thrust mode, e.g., from the front of the turbofan engine towards the rear of the turbofan engine. The air or gas passing through the cold flow air duct, illustrated at 15 in FIG. 1, passes over the surface of internal panel 5 and over a deflector 8. Each thrust reverser door 7 has an interior door panel 11 which is connected to the exterior door panel 9 via brace 12 and a door air deflector 13. Door air deflector 13 extends radially inwardly past the surface of interior panel 11 such that, when the thrust reverser door 7 is in its thrust reversing position, door air deflector 13 will impart a more forward direction to the air passing through the opening in the turbofan housing. When in its closed, forward thrust position, the thrust reverser door 7 forms part of the boundaries of cavity 16, which is bounded by the interior door panel 11, the deflector 8, the door air deflector 13 and line 14, which represents the ideal, theoretical surface interconnecting the internal panel 5 with the interior portion of the downstream collar portion 3. Cavity 16, as is well-known in the art, creates air flow distortion and perturbations within the cold flow air duct thereby increasing aerodynamic losses and degrading engine performance in the forward thrust operating mode.
Typical pivoting door thrust reversing systems for a turbojet engine are described in U.S. Pat. Nos. 4,410,152 and 4,485,970, as well as French Patent 2,559,838. Solutions for improving the air flow through the cold flow air duct in the forward thrust operating mode ay also own in the art, a typical example of which may be found in U.S. Pat. No. 4,916,895. This patent describes a thrust reverser door having a movable internal segment such that it matches the ideal flow surface when the door is in the forward thrust position.
Another problem encountered by known turbofan thrust reversers is the controlling of the direction and the shape of the air passing through the opening in the turbofan housing. This is of particular importance where the turbofan engine is mounted close to the aircraft structure where it would prove detrimental to have the thrust reversing gases contact the adjacent aircraft structure. Such control is also important to prevent the reingestion of the thrust reversing gases by the turbofan engine. The thrust reverser in French Patent 1,559,838 provides one attempt at a solution to controlling the shape and direction of the thrust reversing gases by providing a particular orientation to the upstream edge of the thrust reverser opening and/or shaping the distal edge of door air deflector. The technique for controlling the lateral and forward deflections of the thrust reversing gases is defined as "fluid-sheet control".